Japanese space telescope views galaxy clusters through Dutch sunglasses

The launch of the Japanese X-ray telescope XRISM is scheduled for Monday. The Dutch space research institute SRON built, with funding from the NSO, among other things, the telescope's filter wheel.

Ingredients of stars
Artist impression of XRISM. Credit: JAXA

XRISM, the X-Ray Imaging and Spectroscopy Mission in full, is an X-ray telescope developed by the Japanese space agency JAXA in collaboration with NASA and ESA. The telescope will observe clusters of galaxies, the largest objects in the universe. These clusters consist of 50-1000 galaxies and a lot of hot gas, which emits X-rays.
Astronomers can study the galaxies with telescopes such as the James Webb telescope, XRISM will map the movement of the gas.
In addition, the telescope looks at the elements that end up in the gas after explosions of stars. These are the ingredients that later form new stars and planets.


The filter wheel developed by SRON. Bron: SRON

Dutch sunglasses
The largest Dutch contribution to XRISM comes from the Netherlands Institute for Space Research, SRON, and consists of the filter wheel, a kind of sunglasses in front of the camera. The filter wheel rotates different filters in front of the telescope's camera. These filters can dim X-rays that are too bright, or block certain wavelengths. In addition, SRON, together with the Dutch company Photonis, has developed an X-ray source on which the detector is continuously calibrated.



Data access and preparation for Athena
The SRON-team that developed the filter wheel and calibration source. Bron: SRON.

This contribution gives Dutch scientists and students access to the unique first data collected by XRISM. After that period, 8% of the observing time is reserved for European scientists and scientists have to compete for observing time.

SRON's contribution to XRISM is part of a long tradition. The Netherlands already has experience with X-ray telescopes through contributions to the ESA telescope XMM-Newton and the NASA Chandra mission. XRISM bridges the gap between these telescopes and the ESA X-ray telescope Athena (launched in the late 1930s). The Dutch community is also closely involved with Athena.

Second try
The Netherlands Space Office has funded the Dutch hardware for XRISM through the ESA Prodex program. XRISM is the direct successor of the X-ray telescope Hitomi, which unfortunately stopped working after a few weeks in 2016 due to a faulty control system. SRON also supplied the filter wheel for Hitomi, with funding from NWO. A large part of the design could be reused.